Carbon materials are used in a wide variety of industries and products. These carbon materials include, for example, graphite powder, graphite fibers, carbon fibers, carbon cloth, vitreous carbon products, and an activated carbon products. Many of the uses of these carbon materials are discussed below.
Graphite powder, in addition to its use as "lead" in pencils, has many uses in a variety of fields, including electrical, chemical, metallurgical and rocket components. Electrodes formed from graphite are used in steel-making furnaces and in the electrolytic production of chlorine, chlorates, magnesium, and sodium. Graphite is also used to make metallurgical molds and crucibles and chemical reaction vessels. In the field of rockets, graphite is used to make rocket motor nozzles and missile nose cones.
Graphite fibers and carbon fibers are similarly used in a variety of applications. Short or chopped fibers are often used as reinforcement in injection moldings, as well as in automotive brakes, where their good abrasion resistance is desired. High-performance graphite or carbon fibers are used in structural composites, particularly composites utilized by the aerospace field. These fibers also see widespread use in sporting goods such as fishing rods, golf clubs, and tennis rackets.
Carbon cloth or mats are simply textile products formed from long fibers of carbon or graphite. They are useful in areas such as electrostatic dissipation in carpets or computer-related furniture, electromagnetic shielding, and electrostatic painting of sheet-molded automotive parts. The low thermal conductivity also finds uses the field of rocket components.
Vitreous carbon is used in the manufacture of electrical goods such as electrodes and mechanical goods such as crucibles.
Activated carbon exhibits excellent adsorption properties and is therefore used to improve the color of manufactured chemicals, oils, and fats, to control the color, odor, and taste of water, beverages, and food. These gas-adsorbent carbons are also useful in gas separation processes, the recovery of solvent vapors, air conditioning systems, and gas masks.
Much effort has been expended over the last several decades to modify the surface chemistry of carbon materials. While it is possible to deposit physically adsorbed material onto the surface of a carbon material, permanently changing its surface chemistry is substantially more difficult.
PCT Patent Application No. WO 92/13983 describes a process for modifying the surfaces of carbon-containing materials by electrochemical reduction of diazonium salts. The process is reportedly applicable, in particular, to carbon plates and carbon fibers for composite materials. Carbon-containing materials modified by the process are also described. Electrochemical reduction of diazonium salts containing functionalized aryl radicals to covalently modify carbon surfaces is also described in Delmar et al., J. Am. Chem. Soc. 1992, 114, 5883-5884.
According to WO 92/13983, the process for modifying the surface of a carbon-containing material consists of grafting an aromatic group to the surface of this material by electrochemical reduction of a diazonium salt including this aromatic group. The carbon-containing material is placed in contact with a diazonium salt solution in an aprotic solvent and is negatively charged with respect to an anode which is also in contact with the diazonium salt solution. Use of a protic solvent is reported to prevent the electrochemical process from producing the intended product as a result of reducing the diazonium triple bond to yield a hydrazine.
Despite that technology, there remains a need to modify the surface chemistry of carbon materials and impart desired properties to carbon materials.